Induction electric furnace



Sept. 27, 1932. NORTHRUP INDUCTION ELECTRIC FURNACE Filed July 17, 1929 5 Sheets-Sheet v I l l l I I I I l l l I l I II 3 Sheets- Sheet 2 E. F. NORTHRUP NDUCTION ELECTRIC FURNACE Filed July 1'7. 1929 v e .Illll I ll Illllllllllllt llllll 1:11.11 J I 4 Sept. 27, 1932.

Jllllllllll Sept. 27, 1932. E. F. NORTHRUP 1,379,431

INDUCTION ELECTRIC FURNACE v Filed July 17. 1929 5 Sheets-Sheet s Patented 27, 1932 UNITED s'ra'resv PATEN NEW JERSEY, ASSIGNOR TO AJAX ELECTRO- EDWIN EITOH N ORTHRUP, OF PRINCETON,

T; O F CE THERMIC CORPORATION, OF AJAX PARK,'EWING TOWNSHIP, NEW JERSEY, A COR- PORATION OF NEW JERSEY INDUCTION ELECTRIC FURNACE Application filed July 17,

My invention relates to electric furnaces 4 intended to melt finely divided turnings or above it,

other scrap.

One purpose of my invention is to so charge the turnings as to cause the pressure of the weight of the turnings to compress the turnings in the crucible.

A-further purpose of my invention is to charge the turnings through a stack, thus artificially increasing the height of the column of turnings whose weight normally tends to feed the turnings into the furnace crucible.

A further purpose is to use a stack for charging a furnace and to remove the stack for completion of the operation of melting and pouring, permissibly using the stack during this time for the filling of another furnace crucible.

A further purpose is to preheat the turnings by an inductor coil located at an intermediate point in their passage to the crucible, reducing the percentage of turnings Which still are magnetic after they reach the crucible so as to improve the power factor of crucible inductor coils and to secure nearly uniform magnetic conditions within both the coils.

A further purpose is to'inductively heat" scrap magnetic material at two different points, one on its way to the crucible and the other within the crucible, both While the scrap is under compression by a head of scrap greater uniformity nary heating inductor and for the coils about of power factor correction the melting crucible.

other scrap to be melted as a Weight to make the pile more compact at the lower end and to melt inductively Where the scrap is relatively "current to separate inductors acting upon scrap having different magnetic conditions but part of the same charge, one inductor for I it presents quite a problem.

permitting substantial uniformity, of power factor correction within the prelimr 1929. Serial No. 378,834.

each phase, thus reducing the cost of the machine per unit of powerlfurnished.

Further purposes will appear in the specification and in the claims. i My invention relates both to the methods or processes involved and to apparatus by which they may be carried out..

Figure 1 is atop plan view of one embodiment of my invention. v

Figure 6 is a diagrammatic View showing the swinging of the stack.

In the drawings similar numerals indicate like parts.

lVhere large quantities of scrap metal are handled the remelting of the scrap to recover ternal applied fuels has been quite unsatisfactory and melting by are furnaces has greatly altered the composition of the metal.

In addition to the variation in the chemical composition of the metals or alloys, it has been necessary for are melting that the materials be cabbaged preliminarily. The concentrat on of metal in the loose scrap is very low, reaching a percentage for fine steel turn- Melting by eX- ings less than 5%. of the total bullgand plants A further purpose is to use the turnings or for cabbaging such material arequite eXpensive. The additional cost of handling to ,transport the cabbaged scrap greatly infor cabbaging, transferring the scrap conveniently by electro-magnetic grabs and utilizing a high column of scrap to insure a continuousfeeding to the furnace. crucible and to utilize the pressure due to the Weight of the scrap to condense the scrap in the crucible. The grab transfer of course applies to magnetizable scrap only.

The structure shown is described in illustration and not in limitation and for the purpose only of complying with the statute by explaining the best form of my invention known to me.

For convenience of operation I raise my furnaces above the normal floor level 10 so that the furnaces may be accessible from a platform 11 which is approached suitably at 12. The equipment shown comprises a supporting frame 13 carrying funnel tops. 14 or 14 above the several furnace crucibles 15 and 16 and supporting a crane mast 17. Bracket 18 carries a furnace shaft 19 which may be swung into position beneath either of the- 'funnel charging inlets 14: or 14'. -In either position it spans the space between the funnel inlet and the top of the corresponding crucible 15 or 16. Independently mounted upon the crane mast is shown a bracket 20 adapted to carry a cover 21 or 21 which may be placed over either crucible when the stack or.

shaft 19 has been moved away.

The material to be charged is lifted through any suitable crane, of which the magnet terminal 22 only is shown, and may be dropped into the funnel inlet by release of current in the magnetic clutch, grip or grab of the crane.

The crucible is shown as capable of being tapped through any suitable outlet 23, plugged at 24 so as to permit discharge of the molten content through a gutter 25.

The space 26 surrounding the furnace coil or coils 27 is circumferentially closed at its lower part so as to provide a passage to receive molten metal in case of accidental breakage of or leakage through the crucible.

' At the bottom of this space discharge outlets 28 are closed at the top by fusible plates 29 which will stop a slight flow but which will give way to any considerable flow of molten metal.

As thus far described, the construction of V the platform, framework and taps may be regarded as conventional, but the use of the stack, the moving of the stack into and out of position above the crucible or the crucible from beneath the stack, the capability of using the stack and cover for any of different furnaces, and the use of a safety plate to safeguard the furnace and allow flow of leakage metal away from it are believed by me to be novel and to be of broad application in many other settings than the setting shown.

In Figures 4; and 5 slightly different detail is shown of'the crucible and stack, and conventionally saown furnace windings in novel location and relation are illustrated capable of use with the stack of Figures 1-3, or with any other form of stack and its furnace.

In'Figure 4 inductor coils 27 and 30 are shown conventionally, one surrounding the crucible and the other surrounding the stack and fed from the supply lines 31, 32 and 33 ber of phases than two-phase could be used to supply the coils surrounding the crucible with or without supply to the coils surrounding the stack and the same sources ofcurrent can be used for supplying the stack and crucible coils if desired.

Where the stack is made of electrically conducting material it is desirable to break its circumferential continuit at one or more places to prevent dissipatlon of energy within the stack and such an interruption is shown conventionally. by a vertical slit 34 in the lower part of the wall of the stack.

Obviously there are many'ways by which induced current flow within the stackmay be sufiiciently'prevented so that the current will be confined within the content rather than within the casing or shall. This is of importance because heatin of the finely divided product by heat con activity from the shell would be very slow and inefficient, whereas heating by current induced within the content is rapid and highly effective with high frequency current.

The character of attachment of the funnel inlet in Fi u'res4 and 5 as compared with the earlier gures is not regarded by me as of much importance as the gures are largely diagrammatic and are intended to show suggested forms rather than necessary constructions.

In operation there is no necessity for having an initial pool into which the turnings are forced though such a pool initially or as formed assists in the melting. If the metal were solid the extent of penetration of the induced current within the charge would be very small, but because of the small total volume of metal, a considerable depth of penetration within the metal will occur, heating to great. advantage.

The weight of the column of scrap not only increases the density of the scrap at the lower part of the column so that the current will not be induced in the scrap to as great a depth as would otherwise be the case but greatly improves the contacts of individual parts of scrap with each other to facilitate passage of the current.

Because of the small volume of scrap as compared with the volume of this same scrap when melted, a supply of scrap in the stack high enough to fill the crucible with molten dicate that the metal would involve an excessive height of stack. This is taken care of by progressively feedin quantities of scrap through the same stack ength until the required quantity has been supplied.

As the furnace crucible can be handled and emptied in any way desired after removal of the stack from a position over it, I wish to point out that provision for tapping a stationary crucible is not intended by me to incrucible need be of stationary ecause of the very low concentration of metal in uncabbaged scrap such as turnings the depth of penetration of the induced current within the scrap is relatively very high, too high for good power factor conditions if the frequency were not high. The high frequency is further very beneficial in the very rapid rate of change secured by this frequency, the consequent high rate of power input throughout the content and the improved flow of current across the poor contacts between adjoining fragments of the charge.

WVhereas in previous operations upon scrap, including turnings it has been assumed that it was necessary to have an initial pool of molten metal into which the scrap can be submerged I find that this is not necessary with my invention. Though I could feed my scra into an initial pool, m invention is entire y practical starting witli a furnace substantially freefrom molten metal content and continuing operation until the molten content reaches any desired approach to the full permissible content of the furnace.

In operation, feeding of the turnings or other scrap to the shaft will be stopped when the molten content of the furnace and the anticipated molten metal from the content of the shaft will fill the furnace with molten metal to the desired depth. All of the content is then melted down into the furnace after which the shaft will be moved away from the top of the furnace while the furnace is tapped of its molten content. This can be done whether it be the intention to use the shaft or stack in the filling of an additional furnace in the meantime or not.

The placing of a coil about the lower part of the stackheats the content within the stack to a high degree before it enters the furnace, avoiding the relative chilling of the furnace which would otherwise take'place and reducing the time taken for the melt. Since this coil about the stack may be controlled to operate upon magnetic metal only, by controlling the power input and through it the temperature at which the metal leaves this part of the stack, the inductance of this coil will be substantially constant and the power factor of the circuit feeding this coil may be maintained quite high and nearly free from fluctuation.

a For the same reason that there will be a sists in artificially smaller amount of magnetizable metal within the furnace pool than would otherwise be the case the power factor of the circuit or circuits feeding the coils about the furnace crucible ma be kept high and substantially constant.

efore magnetizable scrap loses its magnetism the frequency used can advantageously be lower than that desirable after it has lost its magnetism.

It will be obvious that the diameter of the crucible and hence the diameter of the stack can be made large enough to avoid induction of current beyondthe center of the charge. Exce t for this desideratum the size of the crucible will be determined largely upon the basis of the desirable size for handling thetype of charge.

In the discussion steel or iron turnin have been contemplated, as the utility of t e furnace will probably be greater for handling a magnetic than for non-ma etic scra but .it is evident that the invention is appllcable also to scrap of non-magnetic metals with considerable benefit though not with all nor the same benefit as in the case of magnetizable charges.

While I have preferred to illustrate m invention by but two slight variations of the same general form, I recognize that my invention can be applied to many different forms and variations and have selected those shown because they are practical, reliable and effective and at the same time well illustrate the principles of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. The method of heating and melting uncabbaged magnetizable scrape, which consists in progressively feeding the scrap in a downward direction under a pressure equivalent to a head in excess of the head obtainable from the furnace and in passing high frequency current about the scrap through separate paths comprising belts spaced along the path of travel of the scrap to induce current wit to preheat it and to melt it, respectively.

2. The method of preheating and melting uncabbaged magnetizable scrap, which consists in advancing the scrap and in separately inducing high frequency current within the scrap through belts of the scrap along its path of travel, the belts being spaced one from the other and located to affect the scrap respectively before and after the scrap loses its magnetism.

3.- The method of preheating and melting uncabbaged magnetizable scrap, which conextending the head of scrap above that of which the furnace is located, in utilizing the additional head secured to compress the scrap and to increase the currentcarrying contact and in inductively causing current to pressed.

pass through the scrap so coin- 4. Ihe method of preheating and melting uncabbaged magnetizable scrap, which con sists in advancing the scrap, in separately inducing high frequency currentwithin the scrap along its path of travel before and after the scrap loses its magnetism and in correcting the power factor .of the supplies for the two induced high frequency currents separately to secure advantage from substantial maintenance of the inductance of the charge at each of the points of induction.

5. The method of heating and melting uncabbaged scrap in a furnace, which consists in utilizing the weight of a mass of scrap above the furnace to feed and relatively compress the scrap and at the same time passing a high frequency electric current about the scrap at a point of relative compression by the mass to take advantage of the increased density and improved contact thus obtained.

6. The method of heating and melting uncabbaged scra within a. coreless furnace, which consists in providing a column of scrap within and above the furnace so that the scrap above the furnace by its own weight progressively increases the density and improves the contact of the individual pieces of scrap within the column and in passing high frequency current about the lower part of the column of scrap above the furnace.

7. The method of heating and melting uncabbaged scrap within a coreless furnace, which consists in providing a column of scrap within and above the furnace so that the scrap above the furnace by its own weight increases the density and improves the contact of the individual pieces of scrap within the furnace and in passing high frequency current about the scrap within the furnace to inductively heat the scrap.

8. The method of heating and melting unc'abbaged scrap within a coreless furnace, which consists in providing a column of scrap within and above the furnace so that the scrap above the furnace by its own weight increases the density and improves the contact of the individual pieces of scrap within the furnace, in passing high frequency electric current about the body of scrap above the furnace and in passing high frequency electric current also about the scrap within the furnace, to separately induce current in the scrap to preheat and melt the scrap.

9. The method of melting uncabbaged scrap in a furnace, which consists in passing high frequency current about the scrap while maintaining a pressure upon the scrap in the furnace considerably in excess of that of a column of scrap having a height correspondingly to the depth of the furnace.

10. In mechanism for melting uncabbaged scrap, a high frequency coreless induction furnace adapted to induce current in the scrap and a stack above the furnace adapted to maintain a head of scrap upon the scrap in the furnace.

11. In mechanism for melting uncabbaged scrap, a high frequency coreless induction furnace and a stack above the furnace adapted to maintain a head of scrap upon that in the furnace and a high frequency coreless furnace inductor for heating the scrap in the stack below a substantial head of scrap.

12. In an induction electric furnace, a'furnace stack adapted to contain a charge, a furnace below the stack and into which charge is fed from the stack, separate inductor furnace coils surrounding the lower part alone of the stack and furnace, respectively, and high frequency electric current supply for the coils.

13. In an induction electric furnace, a furnace stack adapted to contain a charge, a furnace below the stack and into which charge is fed from the stack, separate inductor furnace coils surrounding the lower part of the stack and furnace, respectively, and adapted to induce current in the scrap and high frequency electric current supply for the coils fed from different phases of the same high frequency supply.

14. In an induction electric furnace, a furnace stack adapted to contain a charge, a furnace below the stack and into which charge is fed from the stack, separate inductor furnace coils surrounding the lower part of the stack and furnace, respectively, and high frequency electric current supply for the furnace inductor and electric current supply for the stack inductor lower in frequency than that for the furnace inductor.

15. In a mechanism for melting uncabbaged scrap, a funnel top, a removable furnace stack beneath the top, a coreless induction furnace with which the stack is adapted to cooperate and into whi h it is adapted to feed and high frequency coreless inductor means about the furnace for melting the scrap while it is subjected to the head of scrap within the stack.

16. In mechanism for melting uncabbaged scrap, a funnel top, a removable furnace stack beneath the top, a coreless induction furnace with which the stack is adapted to cooperate and into which it is adapted to feed, high frequency coreless inductor means about the furnace for melting the scrap while it is subjected to the head of scrap within the stack and separate high frequency coreless inductor means for heating the scrap within the stuck on its way to the furnace.

17. In mechanism for melting uncabbaged scrap, a removable furnace stack adapted to hold a feeding charge, a coreless induction fu nace with which the stack is adapted to cooperate and into which it. is adapted to feed, and separate high frequency chargesurrounding means for inducing current within the content of the stack and within the content of the furnace.

18. In mechanism for melting uncabbaged scrap, a furnace stack capable of removal from the furnace and adapted to hold a feeding charge, a coreless induction furnace with which the stack is adapted to cooperate and into which it is adapted to feed, means for displacin the stack and induction means for meltin t e charge within the furnace.

19. n mechanism for melting uncabbaged scrap, a furnace stack adapted to be removed from a furnace, a coreless induction furnace with which the stack is adapted to cooperate and .into which. it is adapted to feed, means for shifting the stack, a cover for the furnace adapted to be placed above the furnace in the absence of the stack and high-frequencyinduction means surrounding the furnace for melting the charge within the furnace.

20. In a device for melting finely divided scrap, a pair of induction. electric furnaces, a'stack common to the pa1r and means for supporting the stack permitting shifting of the stack from a position over one of the furnaces to feed scrap into that furnace to a position over the other furnace to feed scrap into the second furnace.

21. In a device for melting finely divided scrap, a pair of induction electric furnaces, a stack common to the pair, means for su portin stack rom the position over one of the furnaces to feed scrap into that furnace to a position over the other furnace to feed scrap into the second furnace and cover means for the furnaces when the stack is displaced from position over them.

22. In mechanism for melting uncabbaged scrap, a furnace stack adapted to be removed from a furnace, a furnace with which the stack is adapted to cooperate and into which it is ada porting the stac permitting shifting of t stack, a cover for the furnace adapted to be placed above the furnace in the absence of the stack and high-fre uenc -induction means surrounding the stadlr and surrounding the furnace for heating the charge within the stack and for melting the charge within the furnace.

23. In an induction electric melting furn ifie, a crucible, an inductor about the cruci e, the crucible and inductor to form a cavity and having a dischar e openingin the bottom and a cover for t e o ening adapted to be fused with leakage of the furnace charge.

EDWIN F. NORTHRUP.

the stack per'mitting shifting of t e.

ted to feed, means for sulp a casing-about the crucible spaced from V 

